Improvements on SystemServiceManager:

- Renamed some user-related methods to be consistent with the
  equivalent SystemService method it calls.
- Added EventLogs calls on these methods.
- Added warning about renaming strings used by performance tests.

Bug: 168334562
Test: adb logcat -b events | egrep '(I am_crash|I am_user_| I uc_ | I ssm_)'

Change-Id: I4bc883e09a2862b984db1164e12a763fa9ac2014